Injection method

ABSTRACT

A FLUID IS INJECTED INTO ANOTHER FLUID IN THE SHAPE OF A DIVERGING CONE SO THAT CO-CURRENT STREAMLINED FLOW IS INDUCED IN THE OTHER FLUID ADJACENT TO THE CONE. AN APPARATUS WHICH ACHIEVES THIS FLOW PATTERN COMPRISES A VENTURI NOZZLE IN WHICH THERE IS NO EXTRANEOUS FLUID INLET IN THE IMMEDIATE REGION OF THE VENTURI NOZZLE. THE INVENTION IS OF PARTICULAR USE IN THE INJECTION OF A GAS INTO A LIQUID WHEN BUBBLES OF UNIFORM SIZE ARE PRODUCED AVOIDING LARGE BUBBLES WHICH ESCAPE THE LIQUID AND SMALL BUBBLES WHICH TEND TO GIVE RISE TO STABLE AND UNDESIRABLE FOAMS. ANOTHER USE OF THE INVENTION IS IN FLARE STACK CONSTRUCTION IN WHICH THE NOISE OF THE STEAM INJECTORS IS REDUCED BECAUSE OF REDUCED TURBULENCE.

June 11, 1974 M. G. KELHAM INJECTION METHOD Filed Nov. 17', 1969 I n venlor %C//4ZA fia 3a fiAf AM w fl lt M Attorney;

United States Patent Oflice 3,816,515 Patented June 11, 1974 US. Cl. 260-497 A 7 Claims ABSTRACT OF THE DISCLOSURE A fluid is injected into another fluid in the shape of a diverging cone so that co-current streamlined flow is induced in the other fluid adjacent to the cone. An apparatus which achieves this flow pattern comprises a venturi nozzle in which there is no extraneous fluid inlet in the immediate region of the venturi nozzle. The invention is of particular use in the injection of a gas into a liquid when bubbles of uniform size are produced avoiding large bubbles which escape the liquid and small bubbles which tend to give rise to stable and undesirable foams. Another use of the invention is in flare stack construction in which the noise of the steam injectors isreduced because of reduced turbulence.

The present invention relates to a method of injectingv a first fluid into a second fluid and to an apparatus for carrying out the method.

The simplest method of injecting one fluid into another fluid is through an open ended pipe. The jet which leaves the opening in such a case is cylindrical in form and being unstable gives rise to eddy currents and turbulence in the medium through which it is passing. The net effect of the turbulence is to produce a wide range of bubble sizes (gas into liquid) or droplet sizes (liquid into liquid). For many purposes this eflfect is disadvantageous particularly when a gas is being injected into a liquid because the larger bubbles tend to escape from the liquid and the smaller bubbles show an undesirable stability giving rise to foaming. In addition when a gas is injected into another gas or into a liquid the production of noise is an undesirable effect of the turbulence signifying loss of useful energy. We have now found that if the injection takes place through a venturi nozzle the jet leaves the nozzle in the form of an expanding cone which by giving improved momentum transfer induces streamlined and not turbulent flow in the fluid through which the jet is passing, the fluid flowing co-currcnt with the jet. We have also found that interaction at the boundary between the jet and the fluid medium produces bubbles of substantially the same size and that the noise produced is also considerably reduced. The differences in jet form and in the motion induced in the medium through which the jet is passing are shown in the attached diagram portraying flow from an open ended pipe (FIG. 1) and from a pipe fitted with a venturi nozzle (FIG. 2) the dotted lines representing the shape of the jet produced and the arrows the flow induced in the medium. A further advantage of the use of a venturi nozzle we have found is that the jet produced penetrates further than the jet produced by a conventional nozzle, less of the energy of the jet being dissipated in turbulent interaction with the medium.

Venturi nozzles are known in gas ejectors and also in jet mixing devices known as eductors. In this use of a venturi however the region of the pipe immediately before the venturi nozzle contains one or more openings through which extraneous fluid is drawn from outside the pipe by the suction effect of the fluid passing through the venturi. Mixing of the fluid flowing through the pipe to the venturi and the extraneous fluid takes place in the venturi throat and we have found that this detracts from the streamlined conical flow which is necessary for the present invention. Furthermore the energy of the jet flow through the venturi is dissipated by the suction and mixing effects giving rise to an unstable jet of lower penetrative properties. Similarly in the known venturi scrubbers the introduction of a liquid spray into the throat of a venturi through which the gas to be scrubbed is passing causes disruption of and loss of energy from the jet leaving the venturi.

Accordingly the present invention is a method of injecting a first fluid into a second fluid which comprises passing the first fluid into the second fluid as a diverging cone such that co-current streamlined flow adjacent to the cone is induced in the second fluid.

Both gases and liquids may constitute the first or second fluid but the method is of particular value in injecting a gas into a gas, a gas into a liquid or a liquid into a liquid. For example, in flare stack construction steam jets are used to induce a flow of air into a plume of waste gas to provide the oxygen necessary for burning. The use of conventional steam jets is accompanied by a loud noise which can be reduced by use of the present invention. Another illustration of the use of the present invention is in chemical reactors in which a gas e.g. oxygen is injected into a liquid e.g. a hydrocarbon, reaction taking place in the liquid phase. By use of the present invention better and more even gas distribution is achieved. Similarly a mixture of gases e.g. ethylene and oxygen, may be injected into a liquid reaction medium e.g. acetic acid.

The preferred means by which the divergent cone of the first fluid is produced is by passing the fluid through a venturi nozzle in which there is no extraneous fluid introduction in the immediate region of the venturi.

An apparatus for use in the method of the present invention therefore comprises a pipe terminating in a venturi nozzle in which there is no extraneous fluid inlet in the immediate region of the venturi nozzle.

The term extraneous fluid includes fluid identical with that pasing through the pipe to the venturi as well as fluid of different composition. The immediate region of the venturi includes the region in the pipe immediately before the venturi as well as the region up to the end of venturi nozzle. The expression is not intended to exclude the injection of a mixture of fluids to a third fluid in which the mixture is obtained by the introduction of one fluid to another fluid at some distance from a venturi nozzle through which the mixture of fluids is to be ejected.

The size of venturi for use in the present invention is chosen by reference to the rate at which it is desired to pass the first fluid into the second fluid. A suitable venturi may have the following dimensions: a cylindrical inlet of the same diameter as the supply pipe, an entrance cone half angle 25 30, exit cone half angle 515 preferably 7, a cylindrical throat of length substantially half the inlet diameter and a throat diameter substantially one quarter to half the inlet diameter. The exit cone expands to terminate in an exit orifice of the same diameter as the cylindrical inlet to the venturi. The present invention is very suitable for processes in which it is desired to pass a gas into a liquid e.g. at a rate of 10 to litres/ sec. or for the injection of a gas into a gas such as steam into a hydrocarbon stream in a flare stack when /2 to 1 ton of steam may be injected per hour.

An example of an injection device for use in the present invention is shown in longitudinal section in FIG. 3.

A continuous pipe (1) in diameter terminates in a venturi nozzle (2) comprising an entrance cone (3), a tubular throat (4) and exit cone (5). The angle of the entrance cone is 25 and that of the exit cone 7. The throat diameter is inch and its length inch.

In operation the injection device was used to pass air or a mixture of air and ethylene into a liquid such as water at rates up to 25 litres/sec.

What is claimed is:

1. A method of injecting a gas into a liquid which comprises passing the gas into the liquid through a venturi nozzle having no extraneous fluid inlet in the immediate region of the venturi nozzle, said venturi nozzle comprising a cylindrical inlet, an entrance cone angle of 25- 30, a tubular throat, and an exit cone angle of 5 -15 in flow series, the gas entering the liquid as a diverging cone such that co-current streamlined flow adjacent to the cone is induced in the liquid whereby the interaction at the boundary between the cone and the liquid produces bubbles of substantially the same size and produces even gas ditribution Within the liquid.

2' A method according to claim 1 wherein the length of the cylindrical throat is substantially half of the cylindrical inlet diameter, the diameter of the tubular throat is substantially one quarter to one half the cylindrical inlet diameter and the exit cone expands to an exit orifice of the same diameter as the cylindrical inlet.

3. A method according to claim 1 wherein the gas is passed into the liquid at a rate of 10 to 100 liters/sec.

4- A method according to claim 1 wherein the exit cone angle is about 7.

5. A method as claimed in claim 1 in which oxygen is injected into a liquid hydrocarbon.

6. A method as claimed in claim 1 in which a mixture of ethylene and oxygen are injected into a liquid reaction medium comprising acetic acid.

7. A method as claimed in claim 1 in which the gas rate is 10 to 100 litres/sec.

References Cited UNITED STATES PATENTS 1,960,013 5/1934 Iacobsen 26177 2,012,315 8/1935 McIntire 261-77 X 2,394,199 2/1946 Myers 261-77 X 3,276,698 10/1966 Wood 261-121 R 3,253,020 5/1966 Schaeffer 260-497 A 2,592,904 4/ 1952 Jackson 261124 X U.S. Cl. X.R. 

